A helical chain-like organic-inorganic hybrid arsenotungstate with color-tunable photoluminescence

A 1-D infinite helical chain-like organic-inorganic hybrid arsenotungstate Na4H8[{Pr(H2O)(2)}(2){As2W19O68}{WO2(mal)}(2)]center dot 24H(2)O (mal = malate) (1) was prepared, which was characterized by elemental analyses, thermogravimetric (TG) analyses, IR spectroscopy, powder X-ray diffraction (PXRD) and X-ray single-crystal diffraction. Structural characterization revealed that 1 comprises the organo-functionalized [{As2W19O68}{WO2(mal)}(2)](18-) polyanions hinged together by the Pr3+ ions forming a 1-D infinite helical chain-like architecture. The malate ligand may play a vital role to stabilize the structure of 1 by the formation of the five-membered W-O-C-C-O chelate ring. Solid state photoluminescence reveals that 1 features excitation wavelength-dependent emission properties, achieving a reversible emission color switching simply via changing the excitation wavelength. Time-resolved emission spectroscopy (TRES) indicates that the photoexcitation O -> M ligand to metal charge transfer (LMCT) of arsenotungstate fragments can sensitize the Pr3+ ions through intramolecular energy transitions in 1.